1. Field of the Invention:
The present invention relates to a method of producing a motor frame with heat radiation fins used for an electric motor.
2. Background Art:
Generally, the operation of an electromagnetic apparatus causes a temperature rise due to internal power loss. In an electric motor, a plurality of heat radiation fins are attached onto the outer circumferential surface of the frame body to increase the surface area of contact between air and the frame body. The heat radiation fins function to release heat produced in the motor to the outside to thereby prevent the temperature rise.
The motor frame used for the electric motor of this kind is manufactured by disposing heat radiation fins on the outer circumferential surface of the frame body previously formed in a cylindrical shape and by bonding the heat radiation fins to the frame body by projection welding. In this case, the projection welding is carried out simultaneously for a pair of the heat radiation fins placed on the frame body at positions about 180.degree. apart from each other in the circumferential direction of the frame body so that a thermal stress produced in the frame body is dispersed.
The frame body is provided with a base portion for stably positioning the electric motor in place and a hanger ring for hanging and transferring the electric motor. In this case, it is unnecessary to bond by welding one of the pair of the heat radiation fins at the position where the base portion or the hang ring is formed. Therefore, the heat radiation fins are not simultaneously welded at symmetric positions with the result of a problem of the thermal stress produced in the frame body.